Apparatus for condensing exhaust steam from a steam turbine power plant

ABSTRACT

Power plant turbine exhaust steam is condensed in a direct contact condenser by the quenching action of a subcooled portion of the condensate.

United States Patent 1191 Larinoff 1 Sept. 25, 1973 APPARATUS FOR CONDENSING EXHAUST [56] References Cited STEAM FROM A STEAM TURBINE POWER UNITED STATES N S PLANT 3,660,980 5/1972 Knirsch 60/95 R [75] Inventor: Michael W. Larinoff, Houston, Tex. FOREIGN PATENTS OR APPLICATIONS Assigneel Hudson Products Corporativn, 1,109,185 6/1961 Germany 165/110 Houston, Tex. 344,736 4/1960 Switzerland 60/95 R [22] Filed: Oct. 12, 1971 Appl. No.2 188,117

US. Cl 165/110, 60/96 R, 165/107,

261/131 Int. Cl. F28b 3/04, F28b 11/00 Field of Search 165/110, 111, 107;

Primary ExaminerAlbert W. Davis, Jr. Attorney-W. F. Hyer et al.

[57] ABSTRACT Power plant turbine exhaust steam is condensed in a direct contact condenser by the quenching action of a subcooled portion of the condensate.

3 Claims, 3 Drawing Figures PATENTEU 3, 760 .871

. I saw 1 or 2 PATENTEB SEPZ 51975 SHEET 2 OF 2 V/IZ Vi (OPfN) densing exhaust steam from a steam turbine power plant. More particularly, it relates to improvements in apparatus of this type in which the steam is condensed in a direct contact condenser by the quenching action of a subcoole'd portion of the condensate which is returned to the condenser through conduit means forming a closed system therewith.

In such apparatus, a portion of the condensate is drawn from the condenser outlet and circulated by a pump in the conduit means through an atmospheric heat sink, such as an air-cooled heat exchanger, arranged therein downstream of the pump, and a means is arranged in the-conduit means intermediate the heat exchanger and the condenser for restricting flow therethrough so as to maintain a desired positive pressure in the system upstream thereof in contrast with the subatmospheric pressure maintained within .the condenser downstream thereof. As well known in the art, apparatus of this typeis especially useful in environments where there islimited water supply for consumptive uses in the removal of turbine-exhaust waste heat.

The power output and thermal efficiency of the steam turbine power plant as a whole, is dependent onthe condenser pressure being kept'low i.e., the lower the condenser pressure, the higher the output and efficiency of the plant. Condenser pressure is in turn a function of the steam load, the ambient air temperature and the circulating fluid rate. Obviously, little can be done about the first two factors, so that ordinarily the condenser pressure will rise, and thus plant output and efficiency will fall, during the summer when ambient temperatures are normally at their highest.

An object of this invention is to provide apparatus of this type in which the condenser pressure can nevertheless be lowered during the summer with a system that employs fixed speed circulating water pumps. I

A further object is to provide such apparatus which requires only relatively minor modifications to standard components of apparatus of this type, and which is relatively inexpensive to manufacture and foolproof in operation. 1 t I A i These and other objects are accomplished, in accordance with the illustrated embodiment of my invention, by improved apparatus which utilizes known hydraulic pump characteristics to provide increased flow rate through the system, which in turn lowers pressure within the condenser below that possible without my improved apparatus. More particularly, I take advantage of the fact that the flow capacity of a pump increases in a predictable manner with decreases in the total dynamic head of the system in which the pump is operating. Thus, I provide apparatus which controls and maintains hydraulic flow in such a manner as to insure operation at the minimum total dynamic head requirements of the system by automatically lowering and raising the pumping head by an amount corresponding to the rise or fall in condenser pressure. Thus,

when ambient temperatures are high, its possible to reduce condenser pressure by maintaining the pump head characteristics at a desired minimum. 1 For this purpose, the improved apparatus of the present invention includes a means for sensing a decrease or increase of pressure within the condenser and a means responsive to such sensed pressure for automatically increasing or decreasing the circulating flow rate through the conduit means to the extent required to raise or lower the total dynamic head requirements a corresponding amount. Preferably, the means for so raising or lowering the total dynamic head requirements includes the means in the conduit means of the closed system for regulating the existing flow restricting means, because this avoids the necessity for providing additional flow restrictions in the conduit means. Also, the existing flow restricting means is close to the condenser from which its operating signal is derived, so as to simplify the construction and cost of the system and reduce the possibility of malfunctions which might be expected if the flow restricting means and the source of its operating signal were widely separated.

In the apparatus illustrated herein, a means is provided for sensing the position of the flow restricting device of the flow restriction means, and a signal representing its position is combined with a signal representing the sensed condenser. pressure to cause such device to assume a predetermined flow restricting position. Thus, suitable control means may be provided for combining these signals in such a way as to produce movement of the flow restricting device. which brings about the desired change in total dynamic head requirements in unison with the uncontrollable changes that occur in condenser pressure.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is .a diagrammatic illustration of-apparatus constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is a graph illustrating the hydraulic characteristics of the pump in the system; and

FIG. 3 is another graph illustrating the change in position of the flow restricting device responsive to changes in condenser pressure.

With reference now to the details of the abovedescribed drawings, the apparatus is shown in its entiretyin FIG. 1 to include a direct contact condenser 10 having an inlet 11 at its upper end connected to the steam exhaust from the turbine of a steam power plant (not shown), to receive the exhaust steamtherefrom, and an outlet 12 at its lower end through which condensate is discharged. Conduit means 13 connects with the outlet for returning a portion of the condensate to the power plant cycle, and conduit means 14 also connects with the outlet to form a closed system with the condenser for returning the remainder of the condensate thereto intermediate the inlet and outlet. The relative proportions of condensate return to the power cycle and the condenser, respectively, are matters to be determined by those skilled in this art. Also, of course, there may be two or more such condensers, with the conduit means 14 connected thereto in parallel, or with additional conduits connecting them in series so that the condensate from one provides the quenching condensate for the other.

The condenser 10 is of generally conventional construction comprising a large body 15 for receiving steam from the inlet 11 within its upper end and containing condensate at a level 16 in a hot well in its lower end above the outlet 12. In a typical design, headers 17 extend across the upper end of the condenser body 1-5 and are connected to depending pipes 18 carrying spray nozzles 19 therefrom. As will be described more fully to follow, the conduit means 14 has branches 14A and 148 each connected with one of the headers for delivering subcooled condensate to the spray nozzles 19. As well known in this art, the subcooled condensate sprayed from the nozzles 19 will quench the steam known to persons skilled in this art, the arrangement of passing into the condenser body, and thus cause all of 5 the condensate to accumulate within the hot well in the lower end of the body. Obviously, other arrangements of spray nozzles, as well as trays and the like, may be provided within the condenser body for providing the desired steam quenching effect.

A single pump 20 is arranged in the conduit means 14 relatively closely to the condenser outlet 12; however, its obvious that there may be two or more such pumps connected in parallel. This pump is of fixed speed variety and possesses the hydraulic characteristics required to circulate the desired quantity of condensate through the air cooled system to the condenser. Thus, as also well known in the art, it is a hydraulic characteristic of all pumps selected for specific duties that they will generate a total dynamic pumping head equal to the total system resistance at the desired system flow rate. As well known in the art, system resistance depends upon a number of fixed elements in the system, including static heads, pressure requirements within components of the system, and frictional losses. Thus, inasmuch as these factors, making up the total dynamic head requirements, can be predicted, it is possible to select a pump 20 having the required TDH characteristics, as indicated by the curve shown on the graph of FIG. 2. As previously described, and as can be seen from the curve, the pump flow rate increases with decreases in total system resistance.

An air-cooled heat exchanger 21 is arranged in the conduit means 14 downstream of the pump 20, and, as illustrated, includes inclined, upwardly converging banks of finned tubes, with the inlet thereto at the lower end of one bank and the outlet therefrom at the lower end of the other bank. Obviously, however, this is merely illustrative, and the heat exchanger may be positioned differently and comprise any well knownconstruction. Also, of course, it may include a fan or a natural draft tower arranged to cause the flow of air over the finned tubes. Still further, the heat exchanger may comprise two or more separate sections adapted to be isolated by valves for selective use in the system. In any event, the air cooler covers a large ground area and is frequently located a considerable distance from the steam power plant and the condenser for receiving turbine exhaust steam therefrom.

A flow restricting means 22 is arranged within each of the branches 14A and 14B of the conduit means downstream of the air cooler and upstream, but relatively close to, the connection of the branch to the interior of the condenser. As illustrated, each flow restricting means comprises a valve having a flow restricting device which may comprise a gate movable between different flow restricting positions inresponse to reciprocation of a stem 23 on the gate. The stem and thus the gate are caused to move in response to an operator 23A which is responsive to pressure in the condenser, as described to follow.

The details of the valve construction are unimportant to the present invention; and, for example, the means 22 may instead be a butterfly valve having a disc mounted on a rotating stem. In fact, the flow restricting means 22 may instead comprise a hydraulic power recovery turbine having a flow restricting device. As well a turbine in this manner provides a source of shaft or electric power energy, which may be used to assist in the operation of other elements of the system such as the pump 20.

As previously described, valve 22 creates a pressure in the conduit means upstream of it so as to establish a desired hydraulic pressure within the system between it and the pump 20 and degrade the excess pressure energy in the condensate fluid before it enters the condenser 10 where the steam vapor pressure is subatmospheric.

As will be understood, an increase in the pressure within the condenser 10, due for example to an increase in the ambient temperature, will cause a drop in the total resistance or dynamic head requirements of the system. Thus, for example, if the upper curve of FIG. 2 is made to represent the total system requirements during winter months, the lower curve would then represent the system requirements during the summer months. Due to this decrease in the total dynamic pumping head requirement during summer, it is possible to increase th pumping flow rate as indicated by the intersection of the lower total system resistance curve with the Pump TDH curve. For this purpose, valve 22 is caused to open an amount sufficient to increase the circulating flow rate through the system to the extent required to lower its dynamic pumping head requirements an amount corresponding to the increase in condenser pressure. It is this increase in pumping flow rate which improves the power output and thermal efficiency of the power plant. Without the use of this invention, the pump would operate both summer and winter to meet the TDH requirements shown by the upper curve. With the use of this invention, the pump TDH is varied between the limits of the upper curve and the lower curve in accordance with the pressure changes that occur in the condenser.

The information necessary to cause both valves 22 to move to the required extent is supplied to control means including a controller 24, which, in response thereto, produces a signal for transmission to the valve operators 23A. In response to this signal, the valve stems 23 are caused to assume a predetermined position for given condenser pressures, as indicated by the curve on the graph of FIG. 3.

Pressure within the condenser 10 is sensed by a probe 25 or the like extending into its inlet 11, and a signal representing the sensed pressure is transmitted through line 26 to the controller 24. The position of each valve stem 23 is sensed by a transducer 27 located adjacent thereto, and a signal representing this location is transmitted by a line 28 to the controller 24. The two signals are then combined in the controller 24 to produce the above-mentioned signal which is transmitted through lines 29 to the valve operators 23A, which in turn cause the valve stem 23 and thus the flow restricting device of the valve to assume its predetermined position.

The two valves 22 may function alternately, rather than simultaneously, depending upon a second set of signals transmitted through lines 31 and 31A to their operators and/or controller 24 from additional control means including a controller 30. These signals from controller 30 will, in response to given conditions, such as extreme cold weather conditions and/or light turbine loads, override the signals transmitted to the valve operators by the main controllers 24, and thus selectively close and then re -open valves 22, conditions permitting. v p

The controllers 24 and 30 may operate in response to and transmit signals of various type, such as electrical, pneumatic or hydraulic. The construction of the controllers 24 and 30 itself may be conventional, and many instruments for combining and transmitting signals according to predetermined conditions are well known in the art. Also, of course, the operator 23A may be of conventional construction.

Thus, for example, in the event of extremely cold weather or light turbine loads, or both, the system requires only a fraction of the design water flow rate in order to condense the exhaust steam from the power plant. Consequently, it may be possible to remove one or more of several circulating pumps and/or one or more sections of the air cooler 21 from operation in the system. When this occurs, one or more of the valves 22 may be closed by controller 30 and the stem of the operating valves repositioned by controller 24 in accordance with the overriding intelligence from controller 30. Thus, although shown separately, controllers 24 and 30 are in essence two sections of the control means.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

lt wil be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. Apparatus for condensing exhaust steam from a steam turbine power plant, comprising a direct contact condenser for receiving said steam, conduit means forming a closed system with the condenser for returning a portion of the condensate thereto, a pump in the conduit means, an air-cooled heat exchanger in the conduit means intermediate the pump and the condenser, means in the conduit means for restricting flow rate intermediate the heat exchanger and the condenser, means for sensing the steam pressure within said condenser, and means responsive to the rise or fall of the sensed steam pressure for automatically increasing or decreasing the circulating flow rate through the conduit means to the extent required to respectively lower or raise the total dynamic head requirements of the system a corresponding amount.

2. Apparatus of the character defined in claim 1, wherein the means for increasing or decreasing the flow rate comprises means for regulating the flow restricting means.

3. Apparatus of the character defined in claim 2, wherein said flow restricting means includes a flow restricting device, means for sensing the flow restricting position of the flow restricting device, and means responsive to the sensed pressure within the condenser and the sensed position of said flow restricting device to position said device in a predetermined flow restricting position. 

1. Apparatus for condensing exhaust steam from a steam turbine power plant, comprising a direct contact condenser for receiving said steam, conduit means forming a closed system with the condenser for returning a portion of the condensate thereto, a pump in the conduit means, an air-cooled heat exchanger in the conduit means intermediate the pump and the condenser, means in the conduit means for restricting flow rate intermediate the heat exchanger and the condenser, means for sensing the steam pressure within said condenser, and means responsive to the rise or fall of the sensed steam pressure for automatically increasing or decreasing the circulating flow rate through the conduit means to the extent required to respectively lower or raise the total dynamic head requirements of the system a corresponding amount.
 2. Apparatus of the character defined in claim 1, wherein the means for increasing or decreasing the flow rate comprises means for regulating the flow restricting means.
 3. Apparatus of the character defined in claim 2, wherein said flow restricting means includes a flow restricting device, means for sensing the flow restricting position of the flow restricting device, and means responsive to the sensed pressure within the condenser and the sensed position of said flow restricting device to position said device in a predetermined flow restricting position. 